Hi guys i really need help here. i have a doxin 12v to 220v 1000w MSW power inverter. It was broken and i replaced a capacitor on the input of the battery side. but now when i measure even with a true RMS multimeter it only registers about 117v. Could it be that one of the 4 transformers that are chained to give 220v might have failed? Is there a way to test it on the board? And finally can i use it when it only give 120v output instead of 220v? . The cap that was replaced was the bottom left 1 from the photos
Was that with a load on it?
yes, but im using a led light that works even though it is supposed to have 220v it shines on 117v, its quite strange
Maybe it's just set for 115 V output?
These are mostly H bridges. The output floats above ground. Hence when one side is forced permanently to ground for some reason ( short or drive signal), you get 115. Or are you just measuring it wrong?
Oh is it maybe that i need to measure between earth/ground and say live? ATM i am measuring between live and neutral(COM) and i leave my earth/ground unconnected
like i said its working with a 220v light, could it be that its working fine and im just not measureing correctly? As im scared to plug something more valuable in. And how would i connect the earth?
It's not at all surprising that an LED bulb is working.
If you can find one, try testing with an ordinary incandescent bulb. It will not be harmed by a too low voltage (and will probably give a dull red to orange glow at 1/2 voltage).
Okay i will try that, but am i testing it correctly?
I would definitely put a 100W incandescent bulb on it if possible. That would give it a realistic (and mostly resistive) load for testing.
Measure the ac output voltage with a true rms multimeter.
Measure the ac output voltage with a true rms multimeter.
@Lowku said in the original post that he IS using a TRMS meter.
However, I wonder if even a TRMS meter measures a stepped "sine-wave" properly.
I would use an oscilloscope to measure the voltage.
Don't pull much power without connecting the power devices to a heatsink!
Without measures and without schematics, I think it will be very difficult to make a diagnosis.
The only possibility is to do reverse engineering.
the 4 transformers that are chained to give 220v
Are they wired in serie ? What is the output voltage of each of those dc/dc converters ?
Be careful, there is high dc voltage in such a converter, don't try to repair it if you are not an electrician or an electronics engineer qualified to work with power electronics.
Massive overthinking here. I do have an old HF inverter that put the transformers in series, about 35V each. Always thought I could do something with that, but a use hasn't presented itself. This is just another newbie that is measuring line to ground and imagines a problem.
I am measuring from line to neutral/common